Advances in plasma processing have resulted in tremendous growth in the semiconductor industry. A plasma processing system may be comprised of many components. For ease of discussion, the term “component” will be used to refer to an atomic or a multi-part assembly in a plasma processing system. Thus, a component may be as simple as an edge ring, or may be as complex as the entire process module. A multi-part component (such as a process module) may be formed from other multi-part components (such as a vacuum system, a gas system, a power supply system, etc), which may in turn be formed from other multi-part or atomic components.
Over time, one or more components may wear out. Those skilled in the art are aware that worn-out components may cause damage to the chamber and/or damage to the substrate if the worn-out components are not fixed/replaced. One method of identifying which component may have to be replaced may include using a fixed schedule of component replacement. In other words, a useful life period may be identified a priori for each component. The usage of each component may be tracked and when the component reaches the end of its useful life (as predetermined by the fixed useful life schedule), the component may be replaced.
Unfortunately, the method of predetermining the useful life of a component for replace/repair purposes has its limitations. First, the useful life of a component may vary depending upon the environment surrounding the component. In an example, component 1 may be employed in a processing chamber that may experience a different process recipe or mixture of process recipes than component 2. Thus, component 1 may wear out before component 2 even though both components may be of the same make and model.
Thus, with the predetermined useful life method, unnecessary costs associated with taking a processing chamber offline and replacing a component may be incurred even though the component's useful life may not have actually ended. In addition, the predetermined useful life method may not account for the possibility of the component prematurely wearing out before the expiration of its predetermined theoretical useful life. In many instances, the component's deteriorating condition may result in damaged substrates and/or even damage to the chamber and other components within the processing chamber.
One method for determining component wear may involve tracking the evolution of a single parameter, a so-called uni-variate mode. In an example, the health of a component may be monitored by tracking a single parameter measurable by some sensors. For example, the RF bias voltage may be tracked. If the RF bias voltage is above a predetermined threshold, the edge ring, for example, may be deemed to have reached the end of its useful life.
Unfortunately, the uni-variate method also has its limitations. As aforementioned, a given component is monitored by tracking a single parameter. However, the parameter may be affected by influences other than the condition of the given component. In an example, to monitor the condition of an edge ring, the RF bias voltage may be monitored. However, the value of the RF bias voltage may be affected by influences other than just the edge ring condition. For example, the RF bias voltage may also be affected by the deposition on the chamber wall. Thus, when a high RF bias voltage is identified, the high RF bias voltage value may not necessarily be an indication that a problem may exist with the edge ring. Instead, a problem may exist but further analysis may be required before the cause of the problem can be identified.
Another problem with the uni-variate method is that the uni-variate method can be a “go/no-go” method. In other words, the uni-variate method is usually utilized to identify when a fault condition may exist to enable the component to be replaced. However, the uni-variate method may be unable to assist in predicting when (instead of whether) the component may need to be replaced. In other words, in such a scenario the uni-variate method may, at best, be employed to identify a problem and not predict when a problem (e.g., end of useful life) may occur.
Consequently, when a component, such as the edge ring, does actually wear out, a replacement component may not be immediately available. As a result, the processing chamber may have to remain offline until a new edge ring, for example, can be obtained for replacement. Of course, the manufacturing company may opt to always have replacements (such as an edge ring) available. This method of always carrying spare components can become expensive since the manufacturing company has to allocate resources (money and storage space) to have components available even if the components are still in proper working condition.
Another method for identifying component wear may include utilizing a monitoring patch. A monitoring patch is an item that may be placed on a component. The monitoring patch may be placed close to the surface of the component or may be embedded into the component. A component may be considered to be at the end of its useful life if the monitoring patch has worn out, for example. If the monitoringpatch is embedded, the component is considered to be at the end of its useful life when the monitoring patch becomes visible, for example.
There are several limitations with the monitoring patch method. First, a monitoring patch is required for each component that is to be monitored. Thus, if 100 components need to be monitored, a monitoring patch has to be placed on each component. The monitoring patch method can become very expensive and time consuming to implement and monitor depending upon the number of components that may be monitored.
Also, the utilization of a monitoring patch may increase the risk of contamination. The monitoring patch is a foreign object that has to be placed within the processing chamber. As aforementioned, the condition of the processing chamber has to be tightly controlled in order to prevent damage to the chamber and/or damage to the substrate. By introducing one or more monitoring patches into the processing chamber, the processing environment may be altered. In addition, the degree with which the processing environment may have changed due to the existence of the monitoring patches within the processing chamber may be unknown or difficult to measure.
Another limitation of the monitoring patch method is that by placing a monitoring patch onto a component, the mechanical functionality of the component may be compromised. In other words, the mechanical behavior of an edge ring may change with a monitoring patch embedded in the ring. Unfortunately, the extent at which the patch may have altered the functionality of the component may vary since each component and/or each patch may be unique.
Accordingly, a non-invasive method for predicting component wear is desirable.